Leishmaniasis is a parasitic disease found in parts of the tropics, subtropics, South America, and southern Europe. The disease is caused by protozoal parasites of the Leishmania
genus, and spread through bites of infected phlebotomine sand flies. The primary species reported to affect horses include L. braziliensis
and L. siamensis
. There are several different forms of leishmaniasis that affect horses. The most common forms are cutaneous leishmaniasis and visceral leishmaniasis.
- Cutaneous leishmaniasis: Causes skin sores/lesions that consist of papules and nodules that become ulcerated and crust over. Lesions are most commonly found on the horse's muzzle, pinnae, scrotum, neck, legs, and periocular region.
- Visceral leishmaniasis:Affects several of the horse's internal organs (usually the spleen, liver, and bone marrow).
Leishmaniasis is on the list of diseases notifiable to the World Organization for Animal Health (OIE) and is classified as a Neglected Tropical Disease (NTD). There have been several isolated cases of leishmaniasis occurring in horses living in the United States (US). Endemic foci of leishmaniasis exist in Texas, Oklahoma, Ohio, and Florida. November 2012, a pregnant 10-year-old Morgan mare, was diagnosed with leishmaniasis by the University of Florida. The horse had no previous history of travel outside the eastern US. Symptoms presented as sores inside the mare's left ear.
The sand flies that transmit Leishmania
species are only about one third the size of typical mosquitoes or even smaller.